Web tension control mechanism



Aug. 12, 1969 E. H. TREFF 3,460,7

WEB TENSION CONTROL MECHANISM Filed April 13. 1967 5 Sheets-Sheet 1 INVENTOR. ERN6-$T H. TREFF flaw? (CM ATTORNEY? Aug. 12, 1969 E. H. TREFF 3,460,729

WEB TENSION CONTROL MECHANISM Filed April 15, 1967 s Sheets-Sheet 2 w Mui J F G 2 INVENTOR. ERA/587' H. TIPZEFF Aug. 12, 1969 I E. H. TRE-FF 3,460,729

WEB TENSION CONTROL MECHANISM Filed April 13, 196'? 5 Sheets-Sheet 5 ATTORNYS United States Patent US. Cl. 226-42 16 Claims ABSTRACT OF THE DISCLOSURE The extent of respective circumferential pressure engagements between a resiliently deformable surface of a drive transmitting roll and the surfaces of the driving and driven rolls determines the speed of the driven roll which, in turn, advances web material so that the web material is maintained at a predetermined tension. A flapper member associated with air nozzles moves upon a deviation in the tension of the web and thereby actuates a servo-motor to vary the abovernentioned pressure engagements and provide for driving the driven roll at a speed which will compensate for the tension deviation. The drive transmitting roll is supported by eccentrics which are rotated by the servo-motor to bodily move the drive transmitting roll and thereby vary the pressure engagements between the rolls.

The present invention relates to a mechanism for maintaining a moving web at a predetermined tension and, more specifically, relates to a web tensioning mechanism which includes means for sensing a deviation in web tension from a predetermined tension and means for varying the speed of advance of the web in response to the sensing means to compensate for the deviation in the web tension.

It is an important object of the present invention to provide a new and improved web tensioning mechanism which maintains a moving web at a predetermined tension by controlling the speed at which the web is advanced and which is operable to quickly and accurately change the web speed in response to a deviation in the web tension to thereby rapidly correct the tension deviation.

' A further object of the present invention is the provision of a new and improved web tensioning mechanism in which a web advancing roll is driven by a resiliently deformable roll and wherein the pressure engagement between the rolls determines the speed of advance of the web and in which a servo-motor operates to vary the pressure engagement between the rolls in response to a web tension deviation to thereby vary the speed of advance of the web to compensate for the deviation.

A still further object of the present invention is the provision of a new and improved web tensioning mechanism wherein the servo-motor is part of a power amplification system and operates immediately upon receipt of a very small tension deviation signal from the sensing means to quickly correct the web tension.

A further object of the present invention is the provision of a new and improved web tensioning mechanism wherein the sensing means includes a member which moves upon changes in web tension and causes a tension deviation signal to be transmitted through the power amplification system to the servo-motor and effects movement of the actuator member of the servo-motor an amount substantially greater than the movement of the sensing member.

A further object of the present invention is the provision of a new and improved web tensioning mechanism wherein a balanced fluid pressure system is utilized for actuating a servo-motor for controlling the speed of advance of a web and wherein a sensing means including a flapper member associated with a pair of nozzles is movable from a neutral position upon a change in web tension to effect an unbalance of the fluid system which actuates the servo-motor and the servo-motor, in turn, restores the tension of the Web to the desired tension and restoration of the tension, in turn, causes movement of the flapper member toward its neutral position.

A still further object of the present invention is the provision of a new and improved web tensioning mechanism wherein the servo-motor is of the diaphragm-actuated type having pressure zones separated by a diaphragm and wherein each of the nozzles of the sensing means is connected with one of the pressure zones so that upon movement of the flapper member .a change in the pressure in the pressure zone is effected.

A still further object of the present invention is the provision of a new and improved web tensioning mechanism wherein a dancer roll engages the web material and moves in response to changes in the tension of the web material and a pair of nozzle members are associated with each side of the dancer roll and separate flapper members are associated with the nozzles so that the pressure in the pressure zones in the servo-motor is proportional to an average of the web tension at the opposite sides of the dancer roll.

Another object of the present invention is the provision of a new and improved web tension mechanism having a web drive means including a driving roll driven from a motor, a driven roll in driving engagement with the web and a drive transmitting roll rotatably supported by a sleeve member and having a resiliently deformable surface in pressure engagement with the surface of the driving and driven rolls and wherein the web speed is changed in response to a web tension deviation by moving the sleeve member about an axis eccentric to the axis of rotation of the drive transmitting roll which changes the pressure engagement between the resiliently deformable surface and the surfaces of the driving and driven rolls.

These and other objects will become apparent from the following description of a preferred embodiment of the present invention taken in conjunction with the accompanying drawings and in which:

FIG. 1 is a schematic view of a web tensioning mechanism embodying the present invention;

FIG. 2 is a side elevational view of the web tensioning mechanism of FIG. 1 with parts broken away;

FIG. 3 is a sectional view taken approximately along line 33 of FIG. 2; and

FIG. 4 is a perspective view showing part of the web tensloning mechanism embodying the present invention.

The present invention provides a web tensioning mechanism which maintains the tension on a rapidly moving flexible web of material, such as paper. The web tensioning mechanism of the present invention is: capable of use with any web processing equipment, and is particularly adapted for use with a printing press or web folding equipment. The web tensioning mechanism according to the illustrated embodiment is supported in the path of the web intermediate the web supply roll and web processing equipment. The web tensioning mechanism includes a variable speed web drive, and the web tension is controlled by controlling the speed of the web drive. A servo amplification power system is employed to rapidly change the speed of the web drive in response to a web tension deviation signal and quickly provides a web speed which will rapidly restore the desired web tension.

Referring to the drawings, a web tensioning mechanism is shown schematically in FIG. 1 and is designated generally by the reference numeral 10. The web tensioning mechanism 10 is disposed intermediate the supply of the web, shown herein as a roll of paper 12, and web processing equipment not shown. The web processing equipment may be of any form, for example, a printing press or a web cutting and folding apparatus or a combination thereof.

The web tensioning mechanism comprises generally a web drive means 16 through which the web W passes and which is operable to feed the web. The web tensioning mechanism 10 also includes a servo power amplification system 18 which rapidly changes the speed of the web drive means 16 when the tension of web W deviates from a desired or preset tension dictated by the requirements of the web processing equipment. The web tension of web W is continuually sensed by a web tension sensing means 20 which in the illustrated embodiment comprises a dancer roll 22 which engages the web. The dancer roll 22 is supported for deflecting movement by resilient brackets 24 which permits the roller 22 to move in directions indicated by arrow X in response to Web tension. The web tension sensing means 20 is operatively connected to control the servo power amplification system 18 to effect an increase in the speed of the web to compensate for an increase in web tension and to effect a decrease in the speed of the web to compensate for a decrease in web tension. It is understood that the tension on the down stream side of the device is what is being controlled.

In the preferred embodiment the web W is initially advanced into the web tensioning mechanism from the supply roll 12, as described. The web W is fed from the roll 12 under an idler guide roll 25 and through the web drive means 16. The web then passes around an idler roll 26, then wraps around the dancer roll 22, and is then directed under an idler roll 27 to the processing equipment.

The web drive means 16 comprises a driving roll 28 driven from any suitable source of power such as a motor and a driven roll 30. Driven roll 30 cooperates with a pinch roll 32 to form a drive nip 34 therebetween and through which the web W passes and by which the web is advanced. The driving roll 28 and the driven roll 30 preferably have surfaces constructed of hard material, such as steel, and the drive is transmitted therebetween by a drive transmitting roll 36. Drive transmitting roll 36 has a resiliently deformable source 38 and is supported so that the resilient deformablesurface 38 is in pressure engagement with the relatively harder surfaces of the driving and driven rolls 28 and 30. The resiliently deformable surface 38 of roll 36 may be formed of any suitable resilient material such as rubber or a plastic material which will maintain its resiliency for a considerable length of time upon frequent deformation.

The speed at which the driven roll 30 rotates is determined by the circumferential extent of the pressure engagements between the resiliently deformable surface 38 of the drive transmitting roll 36 and the surfaces of the driving and driven rolls 28 and 30 respectively. The angular velocity of the driven roll 30 is changed by changing the circumferential extent of engagement between the resiliently deformable surface 38 and the driven roll 30, and the extent of engagement between driving roll 28 and drive transmitting roll 36. The greater the extent of circumferential pressure engagement between the resiliently deformable surface 38 and the driven roll 30, the greater will be the angular velocity of the driven roll 30 and the lesser the extent of circumferential pressure engagement between driving roll 28 and surface 38 the greater will be the angular velocity of drive transmitting roll 36, both of which in turn increases the speed of the web W. The extent of circumferential engagement between the rolls is changed by a servo-motor means 40, forming a part of the power system 18.

The servo-motor means 40 comprises a pressure tight housing 42 which provides an interior pressure chamber which is divided into pressure zones 44 and 46 by a diaphragm member 50. The diaphragm member 50 is suitably connected to the housing 42 so as to separate the pressure zones 44 and 46. An actuator rod 52 is suitably connected to the diaphragm 50. When the pneumatic pressures in zones 44 and 46 are substantially equal so that there is equal pressure being applied to opposite sides of the diaphragm 50, the actuator rod 52 of the diaphragm 50 does not move. When the pressure in one of the pres sure zones 44, 46 changes, an imbalance of pressures in the pressure zones results, and the diaphragm 50 flexes or moves toward the zone having the lower pressure and effects a corresponding movement of actuator rod 52. Movement of diaphragm actuator rod 52 effects a movement of the drive transmiting roll 36 to simultaneously increase and decrease the circumferential pressure engagement with the rolls 28 and 30- respectively, or vice versa depending upon the direction in which the actuator rod 52 moves.

.The actuator rod 52 is connected to move the drive transmitting roll 36 by means of a lever 54 pivotably connected to the end of rod 52. The lower end of lever 54 carries an eccentric bearing 56 upon which the roll 36 is mounted for rotation, Movement of lever 54 in the direction indicated by the arrow Y results in movement of the bearing 56 about an axis A eccentric to the axis of rotation B of roll 36 and changes the pressure engagement relationships between the resiliently deformable surface 38 and the relatively harder surfaces of the driving roll and driven rolls 28 and 30.

The pressure in pressure zones 44 and 46 is controlled by a pneumatic circuit 60 which is part of the servo amplification system 18. The circuit 60 includes a suitable source of air under pressure designated generally 62. The pressure source 62 may comprise a motor which drives an air compressor and the discharge of the air compressor is connected to an air conduit 64. The air pressure in conduit 64 is regulated by a manually adjustable automatic regulating valve 66. The pressure in conduit 64 is divided into conduits 68 and 70 which provide separate air conduits to the pressure zones 44 and 46 of the servomotor 40. Each of the conduits 68 and 70 has associated therewith a pair of nozzles 68a, 68b, and 70a, 70b (FIG. 4). The nozzles 68a, 70a are located adjacent one side of the dancer roll 22 and the nozzles 68b, 70b are located adjacent the other side of the dancer roll 22, as shown in FIG. 4. These nozzles are open to the atmosphere and provide for a continuous calibrated bleed-off of the air pressure in conduits 68 and 70 to the atmosphere. As will be apparent hereinbelow, the deflection of the dancer roll 22 of the web sensing means 20 operates to control the rate of air pressure discharge from the bleed-off nozzles 68a, 68b, 70a and 70b. The quantity of air metered to conduits 68 and 70 is controlled by tension setting valve 90 and the system calibrating valve 91 which essentially operate as fixed orifices at any predetermined tension set point. The nozzles and valves cooperate to perform a pneumatic function similar to their electrical counterpart the Wheatstone bridge. By controlling the air pressure bleed-off in conduits 68 and 70 the air pressure in pressure zones 44 and 46 of the servo-motor 40 is thereby regulated.

In the illustrated embodiment, a pair of nozzle blocks 74 and 76 support the discharge ends of nozzles 68a, 70a and 68b, 701), respectively, in spaced opposed relationship. The nozzle blocks 74, 76 support flapper valve members 80, 82 respectively. The flapper valve members 80, 82 are preferably flat plates constructed of spring material and are secured at their upper end as viewed in the drawings to the nozzle block 74, 76 by suitable fasteners. The valve members 80 and 82 extend between the opposing ends of the associated nozzles and their lower ends terminate below the nozzle block. The valve members 80, 82 are connected at their lower ends to journals 84 and 86 respectively which support the opposite ends of the dancer roll 22 for rotation by adjustable linkages 88, 89 respectively.

The valve members 80, 82 have a neutral position which is the position shown in FIG. 1 and wherein the plates 80, 82 are substantially equally spaced from the discharge ends of the opposing nozzles. Movement of the valve members 80, 82 toward the nozzles 68a and 68b respectively, reduces the air pressure bleed-off from conduit 68, causing a corresponding increase in the air pressure in conduit 68 and in pressure zone 44. The control pressure provided by conduit 70 in zone 46 at this time decreases. These changes in pressure actuate the servo-motor means 40 to move the rod 52 and lever 54 to the right as viewed in FIG. 1, thereby increasing pressure engagement between the resiliently deformable surface 38 and the driven roll 30 and decreasing pressure engagement between driven roll 28 and surface 38. The described condition exists when the dancer roll and in particular the journals 84 and 86 move to the right as viewed in FIG. 1 as a result of increased web tension or deviation of the web tension in excess of the preset web tension. The increased pressure engagement between rolls 30 and 36 and decreased pressure engagement between rolls 28 and 36 will increase the angular velocity of driven roll 30 in proportion to the increase in web tension from the preset tension and will increase the speed of the web W to reduce the tension to the preset tension. As the web tension is decreased, of course the dancer roll 22 moves back toward its initial position and the pressures in zones 44, 46 tend to equalize, which does occur when the desired tension is restored to the web. As an operators convenience, a pressure gauge 69 may be provided in conduit 68. The gauge 69 can be calibrated to provide at all times a direct reading of the actual web tension on web W.

On the other hand, if the valve members 80 and 82 move toward the nozzles 70a and 701), the air pressure in zone 46 will be correspondingly increased causing the diaphragm actuator 48 to move the rod 52 and lever 54 to the left as viewed in FIG. 1. The described movement of lever 54 reduces the pressure engagement between rolls 30 and 36 and increases the pressure engagement between rolls 28 and 36 and thereby reduces the speed at which the web W is driven. This latter described condition exists when there is a reduction in the web tension and which is corrected by slowing the web speed until the web tension increases to the preset tension.

As is apparent from the above, the pneumatic power circuit 60 is set up to provide balanced pressures in zones 44 and 46 when the web tension is at the desired tension. The circuit 60 becomes unbalanced when the web tension deviates in either direction and quickly changes the differential pressure acting on opposite sides of the diaphragm 50. The quick pressure change results in a fast change in the velocity of the driven roll 30 to correct the deviation. The change in velocity of driven roll 30 is proportional to the tension deviation since the valve means 72 provides a differential pressure in zones 44 and 46 which is proportional to tension deviation.

The desired operating condition of circuit 60 is adjusted at start-up by adjusting the pres-sure in conduit 70 by operation of valve 90. By adjusting valve 90 a control pressure can be established in pressure zone 46 which is proportional to desired tension about which the entire system operates. Web speeds are produced which provide the desired tension which in turn provides the pressure in conduit 68 and zone 44 which balance pressure in zone 46. With the pressures in zones 44 and 46 balanced to provide the preset tension, the pressure in zone 46 becomes the main control pressure about which the pressure in zone 44 increases and the pressure in zone 46 decreases when there is an increase in web tension, and vice versa when there is a decrease in web tension. Hence when the pressure in zone 44 provided by conduit 68 is equal to the pressure in zone 46 provided by conduit 70 the web is being driven by the web drive means 16 at such a speed in relation to the web processing rate of the processing equipment to provide the preset tension required by the web processing equipment. When the web tension increases the support arms 24 deflect and move the journals 84 and 86 to the right as viewed in FIG. 1 which causes a corresponding rightward movement of the valve plates 80, 82. The resulting pressure ditferential acting on opposite sides of the diaphragm 50 causes an increase in torque transmitted to the driven roller 30 and increases the speed of the web. If there is a reduction in the web tension, the journals 84 and 86 for the dancer roller 22 moves to the left as viewed in FIG. 1 causing the valve members '80, 82 to move to the left as viewed in FIG. 1. This differential in pressure created thereby produces movement of the diaphragm 50 to the left and reduces the angular velocity of the driven roller 30 an amount which corrects the web tension deviation.

The pneumatic power circuit 60 according to the present invention in a sense averages the web tension across the width of the web W. When there is a different tension deviation across the web, the power circuit 60 provides a change in web speed in accordance with the average of the tension deviations. A differential in the tension across the web W results in differential deflection of the journals :84, 86. The differential deflection of the journals 84, 86 provide a corresponding differential movement of the valve members 80, '82. The differential movement of the valve members of course provides a differential bleedoff of air pressure from conduits 68 or 70, depending upon whether the deviation is above or below the preset tension. The differential bleed-off reflects an average deflection of the dancer roll 22 since the air pressure provided in the associated pressure zone is always additive of the air pressure discharged from each of the associated pair of nozzles. The averaging of the tension deviation provides for change in speed of the driven roll 30 which will correct the average deviation of web tension.

The amplification function of the power system 18 provides for the application of considerable force by the servo-motor means 40 on the drive transmitting roll 36 as a result of a small change in web tension. In fact, the power amplification system according to the present invention has been found to have a loop gain of greater than one and approximately ten times that of a comparable mechanical system. The servo power amplification system 18 in addition to having a fast response is easier to regulate than an analogous mechanical linkage system.

The response time of any speed change is affected by the mechanical linkage involved. The present invention minimizes the mechanica linkage necessary to change the position of the drive transmitting roll 36. The mechanical linkage employed by the web tensioning mechanism 10 for moving the roll 36 as shown in detail in FIG. 4. As noted above, the drive transmitting roll 36 is supported for rotation by eccentric bearing 56. The eccentric bearing 56 comprises a pair of eccentric sleeves 96a and 96 keyed to a shaft 98. The ends of shaft 98 are rotatably supported on a pair of spaced brackets 92 and 94 by suitable bearings 100, 102. The sleeves 96a and 96 support the roll 36 for rotation about an axis which is eccentric with respect to the axis of rotation of shaft 98. Antifriction bearing assemblies 104 and 106 support the roll 36 for rotation relative to the sleeves 5'6 and 96. Preferably sleeve 96a is formed as an integral part of lever 54 and movement of lever 54 by the servo-motor 40 pivots the sleeves 96a, 96 and shaft 98 as a unit about the axis of shaft 98. Since the axis of rotation of roll 36 is eccentric with respect to the axis of rotation of shaft 98, the aforedescribed movement of lever 54 bodily shifts the roll 36 toward and away from the axes of rotation of the driving and driven rolls 28 and 30.

The brackets 92 and 94 are mounted for pivotal movement about the axis of a shaft 110, shown best in FIG. 2. Shaft 110 is supported for rotation in the side plates of the frame of the web tensioning mechanism 10, The brackets 92 and 94 also carry the servo-motor means 40 and the pinch roll 32. Pivoting of the brackets moves the drive transmitting roll 36, pinch roll 32, and servo-motor means 40 as a unit relative to rolls 28 and 30. It is necessary to move the resiliently deformable surface 38 of the drive transmitting roll 36 out of pressure engagement with the driving and driven rolls 28 and 31 when the mechanism is not in operation to prevent permanent deformation of the resiliently deformable surface 38. Moving pinch roll 32 away from cooperating driven roll releases the web W from the driving nip 34 and also permits threading the web W through the driving nip 34 at start-up of the web feeding operation.

The servo-motor means is supported on bracket 92 by a suitable support member 112. The pinch roll 32 is restrained to correct alignment on the free ends of brackets 92 and 94 by suitable bearing means 114. As shown it is free to be forced into contact with driven roll 30 by gravity and the tension in the web W. Threaded member 115 allows adjustment of clearance between roll 39 and roll 32 when brackets 92 and 94 are raised to the inoperative position for threading of the web.

The brackets 92 and 94 are pivoted about the axis of shaft 110 by a fluid motor 116. The motor 116 is pivotably supported at its lower end to the frame of the drive mechanism 10 and has a piston rod 117 attached to a lug 118 depending from bracket 92. Suitable conventional controls may be provided for operating the hydraulic motor 16 to pivot the brackets 92 and 94 and move the rollers 36 and 32 toward and away from the rolls cooperating therewith.

The motor 116 is operated to move the brackets 92 and 94 downward into the position illustrated in FIG. 3 and wherein the drive transmitting roll 36 is in pressure engagement with the cooperating driving and driven rolls 28 and 30. The extent of initial pressure engagement between the resiliently deformable surface 38 and the relatively harder surfaces of the cooperating rolls 28 and 30 can be set by an adjustment means 119. Adjustment means 119 comprises threaded members 120 and 121 supported respectively in base members 122 and 123. Heads 120a and 121a of the adjustment bolts 120 and 121 engage the underside of the brackets 92 and 94, respectively, and limit the lowermost position to which the brackets can be moved by operation of the motor 116. Lock nuts 124 and 125 are threaded onto the threaded bolts 120 and 121 and fix the position of the bolt heads 120a and 121a relative to support blocks 122 and 123. By appropriate adjustment of the adjustment means 119, the initial pressure engagement between the resiliently deformable surface 38 of roll 36 and the surfaces of rolls 28 and 30 can be set.

The web tensioning mechanism 10 also provides for adjustment of the extent of relative circumferential engagement between the resiliently deformable surface 38 of the drive transmitting roll 36 and the surfaces of the rollers 28 and 30. The adjustment is accomplished by providing a pair of sleeves 128 which mount the brackets 92 and 94 on shaft 110. The sleeves 128 have a central axis which is eccentric with respect to the axis of rotation of shaft 110. Turning sleeves 128 relative to shaft 110 shifts the brackets 92 and 94 and roll 36 relative to the driving and driven rolls 28 and 30 and changes the extent of circumferential engagement between the rolls.

Prior to operation of the mechanism 10, the pressure engagement between the drive transmitting rolls 36, the driving and driven rolls 28 and 30 and pinch roll 32 and driven roll 30 is adjusted by manipulation of adjustments 115, 119, and 128. Also the valve members 80 and 82 are adjusted to their neutral position by adjustment of the adjustable linkages 88 and 90 which connect the valve members 80 and 82 to the journals 84 and 86 of the dancer roll 22. The air pressure of the system is set by adjusting valve 66 and by adjusting tension setting valve 90 in the air conduit 70 which provides the control pressure in the pressure zone 46 which is balanced by the pressure in chamber 44 when the dancer roll 22 is not deflected away from its running position. Once the web tension mechanism 19 is set up, the operation commences as described and any deviation in the web tension from the tension preset by the described adjustment of the mechanism is rapidly corrected by changing the speed of the web drive 16. When the web processing equipment is shut down, the hydraulic motor 116 is operated to pivot the brackets 92 and 94 about the axis of shaft so as to move the resiliently deformable surface 33 of the drive transmitting roll 36 out of pressure engagement with the rolls 28 and 3t} and the pinch roll 32 out of pressure engagement with the driven roll 30.

Having described my invention, I claim:

1. A mechanism for maintaining a moving web at a predetermined tension comprising means for advancing the web, sensing means for sensing a deviation in web tension from the predetermined web tension, and means for varying the speed of advance of the web in response to said sensing means to compensate for said tension deviation, said means for advancing the web material comprising a driven roll in driving engagement with the web material, a driving roll and a drive transmitting roll having a resiliently deformable surface in respective pressure contact with the surfaces of said driving and driven rolls to transmit torque therebtween, the torque transmitted between said rolls being a function of the respective pressure engagements between said rolls, and said means for varying the speed of advance of said web comprising a power amplification servo-system means for varying said pressure engagements and including a servomotor means responsive to said sensing means, said servomotor means having an actuator operatively connected with at least one of said rolls to effect movement thereof to vary said pressure engagements upon a deviation in the tension of the web, a power system for effecting operation of said servomotor means, and control means in said power system and operatively connected with said sensing means for actuation upon the occurrence of a deviation in web tension and upon actuation effecting operation of said servomotor means.

2. A mechanism as defined in claim 1 wherein said power system is a balanced system when the web tension is at the predetermined tension and wherein said sensing means comprises a dancer roll engageable with the web and movable upon changes in web tension and means responsive to movement of said dancer roll to effect an unbalance of said system and energization of said servo-motor.

3. A web tensioning mechanism as defined in claim 1, wherein said servo-motor means includes a fluid responsive servo-motor having pressure Zones separated by an actuator member and said power system includes means for providing equal pressures in said pressure zones when the tension of the web is at the preset tension and diiferent pressures in said pressure Zones when the web tension deviates from the preset tension.

4. A web tensioning mechanism as defined in claim 3, wherein said means providing equal pressures comprises separate fluid nozzles for continuously by-passing fluid from each of said pressure zones and a flapper valve member movable in response to a deviation in web tension to change the fluid pressure flow through at least one of said fluid nozzles, thereby providing a fluid pressure differential in said pressure zones of said servomotor means.

5. A mechanism for maintaining a moving web at a predetermined tension comprising means for advancing the web, means for sensing a deviation in web tension from the predetermined web tension, and means for varying the speed of advance of the web in response to said sensing means to compensate for said tension deviation, said means for advancing the web material comprising a driven roll in driving engagement with the web material, a driving roll and a drive transmitting roll having a resilient- 1y deformable surface in respective pressure contact with the surfaces of said driving and driven rolls to transmit torque therebetween, the torque transmitted between said rolls being a function of the respective pressure engagements between said rolls, and said means for varying the speed of advance of said web comprising means for varying said pressure engagements and including a servomotor means responsive to said sensing means and operable to vary said pressure engagements upon a deviation in the tension of the web, a power system for effecting operation of said servomotor means, said servomotor means including a fluid responsive servomotor having pressure zones separated by an actuator member, said power system including means for providing equal pressures in said pressure zones when the tension of the web is at the preset tension and different pressures in said pressure zones when the web tension deviates from the preset tension, said means providing equal pressures comprising separate fluid nozzles for continuously bypassing fluid from each of said pressure zones and a flapper valve member movable in response to a deviation in web tension to change the fluid pressure flow through at least one of said fluid nozzles, thereby providing a fluid pressure differential in said pressure zones of said servomotor means, said power system including a source of air under pressure and each of said fluid nozzles comprising an air discharge nozzle supported in spaced opposing relationship to the other nozzle to bypass air to the atmosphere, and said flapper valve means comprising an elongated valve member having a portion thereof located between said discharge nozzles and in the streams of air discharged therefrom whereby movement of said valve member toward one of said nozzles reduces the rate of air discharged therefrom and increases the pressure in the fluid conduit associated with said one nozzle.

6. A web tensioning mechanism as defined in claim 5, further including an idler roll arranged in the path of the web between said driven roll and web processing equipment and about which the web is wrapped, means supporting said idler roll for movement in proportion to the tension of the web and means connecting said flapper valve member to said idler roll for movement in proportion to movement of said idler roll.

7. A web tensioning mechanism as defined in claim 6, wherein said support means for said idler roll provides for skewing movement of said idler roll when tension of the web is non-uniform across its width and wherein a second flapper valve member is operatively connected to said idler roll at a location spaced from the location at which said other flapper valve member is connected whereby said valve members move ditferentially when said idler roll skews and control the flow of by-passed fluid from said separate fluid conduits to provide a pressure in the associated pressure zone of said servomotor which is proportional to an average of the tension deviations across the web.

8. A web tensioning mechanism as defined in claim 7, wherein a second pair of nozzles is associated with said second flapper valve member, each of the nozzles of said second pair of nozzles being in fluid communication with an associated one of the nozzles associated with said other flapper valve member whereby said differential movement of said valve members provides for different discharge of fluid from the communicated nozzles and provides a fluid pressure in the associated pressure zone which is proportional to the average translational movement of said idler roll.

9. A mechanism for maintaining a moving web at a predetermined tension comprising means for advancing the web, means for sensing a deviation in web tension from the predetermined web tension, and means for varying the speed of advance of the web in response to said sensing means to compensate for said tension deviation, said means for advancing the web material comprising a driven roll in driving engagement with the web material,

a driving roll and a drive transmitting roll having a resiliently deformable surface in respective pressure contact with the surfaces of said driving and driven rolls to transmit torque therebetween, the torque transmitted between said rolls being a function of the respective pressure engagements between said rolls, and said means for varying the speed of advance of said web comprising means for varying said pressure engagements and including a servo-motor means responsive to said. sensing means and operable to vary said pressure engagements upon a deviation in the tension of the web, a power system for effecting operation of said servo-motor means, support means mounting said drive transmitting roll for rotation about an axis eccentric to the axis of rotation of said drive transmitting roll, and means interconnecting said support means and said servo-motor whereby operation of said servo-motor moves said support means about the eccentric axis and moves the resilient deformable surface of said drive transmitting roll into difierent pressure engagements with said driving roll and said driven roll.

10. In a web tensioning mechanism for maintaining a preset tension on a web of moving material, web drive means including a driven roll in driving engagement with the web and power means for driving said driven roll, means for changing the speed at which the web is driven including a servo power system for effecting drive of said driven roller at a speed to provide the: preset tension on the web, said servo power system comprising servomotor means operable to change the speed at which said driven roll is driven, a source of fluid pressure, means for directing fluid pressure from said source to said servomotor means, means responsive to web tension and operable to provide a balanced fluid circuit when the tension of the web is at the preset web tension to control said servomotor to provide a first web speed and to provide an unbalanced fluid circuit when the Web tension deviates from the preset tension to operate said servomotor means to provide a second web speed proportional to deviation to correct the tension deviation, said means responsive to web tension including a web engaging idler roll means movable in response to web tension, a first valve member operatively connected to said idler roll means for movement upon a change in web tension at one edge of the Web, a second valve member operatively connected to said idler roll means for movement upon a change in web tension at the other edge of the web, and said valve members being operable to provide a fluid pressure to said servomotor which is proportional to the average of the movements thereof.

11. In a web tensioning mechanism for maintaing a preset tension on a web of moving material, web drive means including a driven roll in driving engagement with the web and power means for driving said driven roll, means for changing the speed at which the web is driven including a servo power system for effecting drive of said driven roller at a speed to provide the preset tension on the web, said servo power system comprising servomotor means operable to change the speed at which said driven roll is driven, a source of fluid pressure, means for directing fluid pressure from said source to said servomotor means, means responsive to web tension and operable to provide a balanced fluid circuit when the tension of the web is at the preset web tension to control said servomotor to provide a first Web speed and to provide an unbalanced fluid circuit when the Web tension deviates from the preset tension to operate said servomotor means to provide a second web speed proportional to deviation to correct the tension deviation, said means responsive to web tension including a Web engaging idler roll movable in response to web tension, a valve member operatively connected to said idler roll and said system upon a movement of said idler roll, said servomotor means including pressure zones separated by an actuator member which is movable in response to different fluid pressures in said pressure zones to change the speed of said driven roll and said power system comprising a source of air presure, conduit means for directing air to said pressure zones of said ser-vomotor means, and said valve member comprising a flapper valve associated with a pair of nozzles open to the atmosphere and thereby controlling the pressure in said pressure zones.

12. A mechanism for use in association with a moving web comprising an idler roll engageable with the web mateiial, means supporting the idler roll for movement in response to tension of the web material, means responsive to the movement of the idler roll and providing a fluid pressure signal in response thereto, said means including a pair of nozzle members through which air pressure is directed and a flapper valve member associated with the nozzle members and providing for air flow from the nozzle members to the atmosphere, said flapper valve member having a neutral position with respect to said nozzle members at which predetermined amounts of air flow from said nozzle members, and means connecting said flapper valve member to said dancer roll for movement therewith from its neutral position and movement of said flapper valve relative to said nozzle members effecting a variance in said air directed to the atmosphere through the nozzles and providing a fluid pressure signal indicating the tension of the web material.

13. A mechanism as defined in claim 12, wherein the air pressure increase in the nozzle member toward which the flapper moves comprises the fluid pressure signal.

14. In a web tensioning mechanism for maintaining a preset tension on a web of moving material, a web drive means including a driven roll in driving engagement with the web, a driving roll drivingly connected to a motor, and a drive transmitting roll having a resiliently deformable surface in pressure contact with the surfaces of said driving and driven rolls to transmit torque therebetween, the torque transmitted to said driven roll and the speed at which the web is driven being a function of the pressure engagement betwen said rolls, means supporting said drive transmitting roll for rotation and translation relative to said driving and driven rolls including a sleeve member, bearing means supporting said drive transmitting roll for rotation on said sleeve member, means mounting said sleeve member for rotational movement about an axis eccentric to the axis of rotation of said drive transmitting roll, and means operable in response to a deviation in web tension for pivoting said sleeve and drive transmitting roll about said eccentric axis to change the pressure engagement between said resiliently deformable surface of said power transmitting roll and the surfaces of said driving and driven roll to provide a web speed which will correct the tension deviation.

15. A web tensioning mechanism as defined in claim 14, wherein said means mounting said drive transmitting roll further includes a pair of spaced brackets, a shaft supported for rotation by said brackets and means fixing said sleeve member to said shaft and said means for moving said sleeve member includes linkage means connected to said sleeve member to move said sleeve about said eccentric axis.

16. A web tensioning mechanism as defined in claim 14, wherein said means for pivoting said sleeve member includes a servo-motor operatively connected to said sleeve member and means for operating said servo-motor in response to deviation of the Web tension.

References Cited UNITED STATES PATENTS 2,934,987 5/1960 Rauline 226-44 X 3,220,347 11/1965 Luehrs 226-30 X M. HENSON WOOD, JR., Primary Examiner R. A. SCHACHER, Assistant Examiner U.S. Cl. X.R. 226-44 

